Flowing from Canada through Washington to Oregon, the Columbia River winds through snow-capped peaks in the northwestern United States, and twists between rolling hills and valleys speckled with desert sage before reaching the spruce-filled coast and pouring into the Pacific Ocean. The country’s second-largest river, it serves as a hub of hydroelectricity and breeding grounds for one of the most coveted types of fish: salmon.

In mid-September, 12 Stanford students gazed into a tributary of the Columbia, Washington’s crystalline Cle Elum River, searching for salmon that had already started clearing algae from shallow sediment to lay their eggs.